AMP-activated kinase reciprocally regulates triacylglycerol synthesis and fatty acid oxidation in liver and muscle:: evidence that sn-glycerol-3-phosphate acyltransferase is a novel target
AMP-activated kinase reciprocally regulates triacylglycerol synthesis and fatty acid oxidation in liver and muscle:: evidence that sn-glycerol-3-phosphate acyltransferase is a novel target
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DOI：
10.1042/0264-6021:3380783
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发表时间：
1999-03-15
影响因子：
4.1
通讯作者：
Coleman, RA
中科院分区：
文献类型：
--
作者：
Muoio, DM;Seefeld, K;Coleman, RA
amp活化激酶（AMPK）是在代谢应激消耗细胞ATP时被激活的，在肝脏和骨骼肌中，活化的AMPK刺激脂肪酸氧化。为了确定AMPK是否可能相互调节甘油脂合成，我们研究了5-氨基-4-咪唑卡酰胺（AICA）核苷存在下的肝脏和骨骼肌脂质代谢，这是一种可渗透细胞的化合物，其磷酸化代谢产物激活AMPK。在培养的大鼠肝细胞中添加AICA核苷3 h后，[C-14]油酸酯和[h -3]甘油向三酰基甘油（TAG）的掺入分别减少50%和38%，二酰基甘油的油酸酯标记减少60%。在离体小鼠比目鱼肌（一种高度氧化的肌肉）中，AICA核苷孵育90分钟可使[C-14]油酸盐掺入TAG减少37%，并使(CO2)-C-14的产生增加48%。当胰岛素存在时，[C-14]油酸氧化比基础条件下低49%，[C-14]油酸并入TAG的比例比基础条件下高62%。AICA核糖体阻断胰岛素的抗氧化和增脂作用，使脂肪酸氧化增加78%，标记TAG降低43%。在C2C12成肌细胞中也观察到类似的脂肪酸氧化和酰基甘油合成结果，在分化的C2C12肌管中，AICA核苷也抑制胞内TAG的水解。这些数据表明，AICA核苷可能抑制sn-甘油-3-磷酸酰基转移酶（GPAT），该酶催化了甘油脂生物合成途径的关键步骤。用AICA核苷培养大鼠肝细胞15和30分钟，线粒体GPAT活性降低22-34%，但不影响微体GPAT、二酰基甘油酰基转移酶或酰基辅酶a合成酶活性。最后，纯化的重组AMPK α 1和AMPK α 2以时间和atp依赖的方式抑制肝脏线粒体GPAT。这些数据表明AMPK相互调节酰基辅酶a向β -氧化和远离甘油脂生物合成的通道，并提供了AMPK磷酸化和抑制线粒体GPAT的有力证据。
AMP-activated kinase (AMPK) is activated in response to metabolic stresses that deplete cellular ATP, and in both liver and skeletal muscle, activated AMPK stimulates fatty acid oxidation. To determine whether AMPK might reciprocally regulate glycerolipid synthesis, we studied liver and skeletal-muscle lipid metabolism in the presence of 5-amino-4-imidazolecarboxamide (AICA) riboside, a cell-permeable compound whose phosphorylated metabolite activates AMPK. Adding AICA riboside to cultured rat hepatocytes for 3 h decreased [C-14]oleate and [H-3]glycerol incorporation into triacylglycerol (TAG) by 50% and 38% respectively, and decreased oleate labelling of diacylglycerol by 60%. In isolated mouse soleus, a highly oxidative muscle, incubation with AICA riboside for 90 min decreased [C-14]oleate incorporation into TAG by 37% and increased (CO2)-C-14 production by 48%. When insulin was present, [C-14]oleate oxidation was 49% lower and [C-14]oleate incorporation into TAG was 62% higher than under basal conditions. AICA riboside blocked insulin's antioxidative and lipogenic effects, increasing fatty acid oxidation by 78% and decreasing labelled TAG 43%. Similar results on fatty acid oxidation and acylglycerol synthesis were observed in C2C12 myoblasts, and in differentiated C2C12 myotubes, AICA riboside also inhibited the hydrolysis of intracellular TAG. These data suggest that AICA riboside might inhibit sn-glycerol-3-phosphate acyltransferase (GPAT), which catalyses the committed step in the pathway of glycerolipid biosynthesis. Incubating rat hepatocytes with AICA riboside for both 15 and 30 min decreased mitochondrial GPAT activity 22-34% without affecting microsomal GPAT, diacylglycerol acyltransferase or acyl-CoA synthetase activities. Finally, purified recombinant AMPK alpha 1 and AMPK alpha 2 inhibited hepatic mitochondrial GPAT in a time- and ATP-dependent manner. These data show that AMPK reciprocally regulates acyl-CoA channelling towards beta-oxidation and away from glycerolipid biosynthesis, and provide strong evidence that AMPK phosphorylates and inhibits mitochondrial GPAT.